Need a rule of thumb for spark plug gap

[Lee_Burough]

I've read that you should have a gap of 0.030 for 30 pounds of boost & 0.035 at stock boost levels. I'm planning to up the boost to a max of 22 PSI next week -with Alchy. What would be optimum plug gap at 22 PSI (in a TTA with AC Delco stock plugs)?

TIA

 

[NastyGn]

I've read that you should have a gap of 0.030 for 30 pounds of boost & 0.035 at stock boost levels. I'm planning to up the boost to a max of 22 PSI next week -with Alchy. What would be optimum plug gap at 22 PSI (in a TTA with AC Delco stock plugs)? TIA

I don't know about any rule of thumb, but with Autolite plugs I found the gap between .032 when the car was stock then to a tight .030 when I went to 10:1 compression (running mid 10's) and as tight as .028. The .030 always run best for me. I then changed over to a full MSD system and stayed with the .030. I can't say I ever seen anyone (in person) gap any smaller than that.

Good Luck

 

[Lee_Burough]

I don't know about any rule of thumb, but with Autolite plugs I found the gap between .032 when the car was stock then to a tight .030 when I went to 10:1 compression (running mid 10's) and as tight as .028. The .030 always run best for me. I then changed over to a full MSD system and stayed with the .030. I can't say I ever seen anyone (in person) gap any smaller than that.

Good Luck

Thanks

I suspect that 0.033 or 0.034 would be good enough with 22 pounds of boost. My problem is that my automatic gapping tool only goes to 0.035....

I'm sure somebady has experience with 22 PSI and they will chime in here

What are the symptoms when the spark blows out from too wide a gap in the plugs?

 

[Lee Thompson]

Too wide a gap

The car will have a intermitten miss under boost.
.032 has always worked for me @ 24 PSI

 

[TURBOV6]

You can use the MSD DIS ignition and gap it at .035

 

[salvageV6]

I had my toolmaker grind a piece of tool stock to .0345" for running up to 24psi. boost worked fine on AC CR43's.

Now I use another tool ground to .032" for 27 peak psi. boost, same plugs.

Pump gas and alky. stock heads and cam. cars.

Gapping to a tight .035 should work fine for your desired boost level.

Sooner or later you will wear down the gapper tool to .034" anyway when gapping them tightly.

 

[Lee_Burough]

I had my toolmaker grind a piece of tool stock to .0345" for running up to 24psi. boost worked fine on AC CR43's.

Now I use another tool ground to .032" for 27 peak psi. boost, same plugs.

Pump gas and alky. stock heads and cam. cars.

Gapping to a tight .035 should work fine for your desired boost level.

Sooner or later you will wear down the gapper tool to .034" anyway when gapping them tightly.

Thanks, that is just the thing I needed to have closure on my issues....I may have my gapping tool modified....I've never used the larger sizes on the gapping tookl, I'll modify one of those to 0.032 or 33.

lee